Pigment granulation

ABSTRACT

The invention relates to a process for preparing organic pigment granules with a particular particle size wherein an organic pigment with a particle size of  0.01  to  10  μm is mixed with water, a C 1 -C 4 alcohol, a C 3 -C 8 ketone or a mixture thereof, a binder and ammonia or a C 1 -C 3 amine and an emulsifier. This mixture is pressed in a continuously operating apparatus through one or more apertures each having a size of  0.2-5.0  mm 2 , the apparatus consisting of at least one conveying device and a shaping section comprising the apertures, and being constructed, and operated with a throughput, such that the pressure in its shaping section does not exceed  10  bar. The granulated product is then dried at a temperature of − 50  to  200 ° C. at atmospheric pressure or under reduced pressure. The invention also relates to pigment granules prepared by the process of the invention, with a particle size of  0.5  to  4  mm, wherein the pigment present essentially has a particle size from  0.01  to  10 μm.

The invention relates to a novel process for granulating organic colourpigments in the presence of aqueous or alcoholic media at low pressure,and to the dust-free pigment granules which can be prepared by thisprocess.

BACKGROUND

Organic pigments consist of very fine particles, of low solubility incustomary solvents, whose dimensions can lie within the range fromsubmicroscopic to about 100 μm. For practical use, organic pigmentshaving approximate particle sizes of from 0.01 to 0.1 μm for transparentforms and from 0.1 to 10 μm for opacifying forms have proved mostsuitable.

The physical properties of the pigment particles are very important totheir use. For instance, very small particles possess an oftenrelatively low light fastness and fastness to weathering and a strongpropensity to agglomeration. Very coarse particles, on the other hand,give rise to undesirably low colour intensities and duller shades. Inthe case of the physical properties, however, particle size distributionand agglomeration play a key part, especially with respect to thedispersibility of the pigments [cf. Farbe und Lack 82/1, 7-14 (1976)].

It is therefore of critical importance for pigments to have a verynarrow particle size distribution, which can usually be achieved byreprecipitation, recrystallization or heat treatment in a polar solvent,at atmospheric or superatmospheric pressure or under a high shear force(U.S. Pat. No. 4,879,380). However, all such pigments, irrespective ofthe narrow particle size distribution, still have the great disadvantageof producing dust. Consequently, when they are used, expensive measures(for example of a workplace safety, ecological or quality assurancenature) are necessary and valuable material is lost.

A very large number of methods have therefore already been investigatedfor converting the pigments into a low-dust or even dust-free form. Ithas however been found that improvements in the dusting behaviour can beobtained in the case of the known methods only, among otherdisadvantages, at the expense of the physical properties of the pigmentparticles, and especially at the expense of the dispersibility.Consequently, the known methods described below are unable to satisfyfully the long-held wish for dust-free organic pigments which continueto have good physical properties.

Known compacting methods, such as compression moulding (tableting orbriquetting), granulation in mix granulators and granulating discs(Aufbereitungs-Technik 12 (1975)) and in formers (Chem.-Ing.-Tech. 49/5,374-380 (1977)), roll granulation (DE-A 27 23 221) or pressuregranulation (Powder Technology 74, 1-6 (1993)) always lead, with pureorganic pigments, to highly agglomerated products having performanceproperties worse than those of the powder. A common feature of thesemethods is that the pigment particles collide with one another with arelatively high force.

Pigments for use in plastics can be incorporated into polymerconcentrates. The pigment is employed as a dry, dusting powder. In thiscontext, high shear forces and temperatures are required to disperse thepigment particles thoroughly, and the physical properties and colourproperties are changed. The resulting polymer grains must in turn bemixed intimately with uncoloured polymer grains for the end use, againunder high shear force, since it is necessary to effect homogeneousdistribution of the pigment particles together with the completelysurrounding polymer. Moreover, the concentrate polymer must becompatible with the other polymer, which is why, for a single pigment, arange of two or more products is required for different plasticsapplications.

Pigments can also be applied to the surface of externally softenedpolymer granules to give spherical particles (U.S. Pat. No. 4,310,483).However, the size of such particles is difficult to control, and thefraction having the desired diameter has to be isolated by sieving. Itis said that the granulating auxiliary can be used in amounts of 2-50%by weight (preferably 5-30% by weight), although it has been found thatgood dispersibility can only be achieved with amounts of at least 15-20%by weight. An additive which can be used in addition to the polymergranules is a wax-like binder whose melting point is typically from 49to 88° C. (U.S. Pat. No. 5,455,288). In the latter case, however, thepigment content is at an unsatisfactorily low level of from 5 to 50%. Inboth cases, collision forces are principally at work in the case of lowshear forces, and the presence of more than 10% by weight of a substanceof low melting point is disadvantageous from the performance standpoint.

Pigments can also be embedded in resins. This is done by first preparinga dispersion of the pigment in an inert solvent (for example water) anda solution of the resin in an appropriate solvent and then mixing thetwo, and precipitating the resin from the solution, either directly inthe course of mixing or else later, the pigment being enveloped by theprecipitating resin. innumerable publications have proposed, as theresin, almost all substances known to have a certain resinous character,including rosin. Various processes in accordance with this principle areknown, for example acid/base precipitations (CS 216 590; IN 156 867;DE-A 33 27 562) and one- or two-phase solvent granulations (U.S. Pat.No. 4,055,439; U.S. Pat. No. 4,208,370). The not entirely satisfactorydispersibility of such resin-embedded pigments can be improved by theuse of special resin mixtures coupled with a very high shear force (U.S.Pat. No. 4,116,924; U.S. Pat. No. 4,168,180). Nevertheless, thepreparation of the pigment dispersion in any case requires intensivemilling, especially when the inert solvent used is an aqueous medium, inwhich case the pigment, however, is comminuted in an undesirable manner.Instead of resins it is also possible to use surfactants (EP 403 917):in this case, although dispersion is made easier, the product is notobtained in a dust-free form but rather in a powder form.

In the case of the acid/base precipitations, the control ofneutralization is a further problem which cannot be solved with completesatisfaction by the method described in DE 33 27 562. When precipitatingwith acid, in fact, the resin does not precipitate in a completelyneutral form, which in many cases causes problems for high-gradeapplications, such as coating operations or the mass colouring ofplastics. In the case of solvent granulations, on the other hand, largeamounts of solvents are required which, disadvantageously, have to berecovered from usually aqueous mixtures. Therefore, the use of acetic orpropionic anhydride as solvent has been proposed (EP 069 617), givingrise to aqueous solutions which can purportedly be used in the chemicalindustry but which, for lack of demand, have to be disposed of atconsiderable cost.

It is also known that colorants can be converted into a low-dustflowable form by spray-drying or in a fluidized bed (EP 039 841; EP 670352). The additives used therein, however, are completely unusable inthe case of pigments that are to be used in high-grade applications suchas the mass colouring of plastics or automotive finishing operations.Moreover, in the case of spray-drying or in a fluidized bed it is hardlypossible to prepare homogeneous granules having a particle size of morethan a few 100 μm (cf. e.g. Chemie-Technik 2116, 72-78 (1992); Arch.Pharm. Chemi, Sci. Ed. 1978/6, 189-201). Furthermore, it is not possibleto fluidize all powders in a fluidized bed (Powder Technology 57,127-133 (1989)), so that it is in no way possible to make generalizeduse of this method.

An improved variant of fluidized bed granulation, especially forpigments, is also known (U.S. Pat. No. 4,264,552) where the particlesize distribution of these granules is very broad and the great majorityof the particles (about half by weight) are smaller than 500 μm.Furthermore, these granules still have an excessive propensity toproduce dust. In Example 2 the use is disclosed of a mixture of 8.2% byweight of Staybelite Resin™ and 0.9% by weight of hydroxypropylcellulose(amounts based in each case on the finished product), in the form of itsammonium salts, as the anionic surfactant.

Water-soluble dyes can be processed with from 5 to 50% by weight of awater-soluble binder to form non-dusting cylindrical granules with adiameter of at least 1 mm (DE-A 2 317 175); according to the examplesthe granules have a diameter of about 1 mm and a length of 5-7 mm. Bymeans of a conveying screw, the homogeneous plastic mass is pressedthrough a perforated disc (perforation diameter 1 mm).

However, water-soluble binders are completely unsuitable for pigmentsthat are intended for use in customary plastics, and organic pigmentstreated by this process are highly agglomerated and have unsatisfactorydispersibility properties. They are therefore not sufficiently suitablefor many applications. The same applies to the powder compression ofwater-moist pigments in a twin-screw extruder at pressures from 10 to 50bar in accordance with the method known from Journal of Powder & BulkSolids Technology 4/4, 27-32 (1980).

Also known are fine, low-dust colorant granules having a very lowcontent of wax-like binder and other foreign substances (EP 424 896). Ofessential importance is the use of a device in which the material fed inis exposed predominantly to severe turbulence and moderate collisionforces coupled with declining shear stresses. This process is suitable,however, predominantly for inorganic pigments, and only one example ofan organic pigment is disclosed: Example 13 uses the monoazo pigmentPigment Red 176, 0.72% by weight of a fatty acid mixture having amelting point of 57-61° C. as the wax, and 50-51% by weight of water(based in each case on the fine granules). The particle size is markedlyless than 1 mm, and a sieving operation is necessary despite therelatively small proportions of coarse particles, which are difficult todisperse, and ultrafine particles, which produce dust.

Other known granules include those which exhibit a large increase involume relative to the initial pigment as a result of the cavities whichare retained on drying (EP 510 392). In this case shaping takes placeexclusively by known methods; for extrusion to strands a residualmoisture content of 50 to 80% by weight is specified. These granules aresaid to be readily dispersible and low in dust, but are brittle and havea low bulk density, with the result that they take up a substantiallygreater volume on transportation and storage. Furthermore, it is verydifficult to obtain products having a precisely reproducible specificweight, and in the case of hydrophobic or apolar pigments this methodproduces unsatisfactory results.

Also known, finally, is a process in which hydrophilic pigments aretransported as aqueous, paste-like agglomerates (U.S. Pat. No.5,328,506). In contrast to extruded “noodles” it is not necessary tocarry out high-energy dispersion of these products later on. However,the process is aimed not at organic pigments but at inorganic kaolinpigments, and the presence of water in the stated amount of 1 to 25% hasan adverse effect on, or may even rule out totally, the use of organicpigments in the vast majority of fields.

Furthermore, as already mentioned, the coarsely particulate pigmentpreparations prepared by some of the known processes are still not,simultaneously, satisfactorily compact, dust-free and/or readilydispersibile. In addition, the desired particle size usually has to beselected by sieving, with particles having a size other than thisdesired particle size (especially the fine fraction) having to be passedback to the process. However, the recycling of the unsatisfactorypigment material causes an additional detrimental alteration to itsphysical parameters, and, consequently, a worsening in the performanceproperties as well.

The aim of the invention was to provide coarsely particulate, extremelydust-free, highly concentrated, readily dispersible and universallyapplicable organic pigment granules in which, apart from the externalaspect, the physical parameters of the pigment particles are changed aslittle as possible relative to the initial pigment powder, unlike theknown granules. The term physical parameters is understood as meaningnot only the abovementioned properties but also all other technicallymeasurable or applications-relevant properties. The intention is thatthese pigment granules should as far as possible be able to be preparedby means of simple and universally applicable methods, in simple,inexpensive and easy-to-clean apparatus, without the addition of organicsolvents to be absolutely necessary and without the need to select theright particles and recycle the rejects.

DETAILED DESCRIPTION OF THE INVENTION

The aim of the invention has been achieved to a particularly surprisingextent by means of the present invention.

The invention relates to a process for preparing organic pigmentgranules with a particle size from 0.5 to 4 mm, which consist of atleast 90% by weight of at least one organic pigment with a particle sizefrom 0.01 to 10 μm and from 0 to 10% by weight of a binder having from 2to 7 mol of carboxyl groups per 1000 g and from 0 to 5% by weight of aneutral emulsifier which does not form ions and which dissolves to givea clear solution in water or a C₁-C₄alcohol at a concentration of atleast 10 g/100 ml, the binder and the emulsifier together accounting fornot more than 10% by weight and all percentages by weight being based onthe overall amount of pigment granules, wherein

[1] the pigment is mixed with 54-92% by weight of water, a C₁-C₄alcohol,a C₃-C₈ketone or a mixture thereof, based on the dry pigment, with thebinder and 0.8-20 mol of ammonia or a C₁-C₃amine, per mole of carboxylgroups in the binder, and with the emulsifier;

[2] this mixture is pressed in a continuously operating apparatusthrough one or more apertures each having a size of 0.2-5.0 mm², theapparatus consisting of at least one conveying device and a shapingsection comprising the apertures, and being constructed, and operatedwith a throughput, such that the pressure in its shaping section doesnot exceed 10 bar;

[3] if desired, the cylindrical granules emerging from the dies areconverted on a rotating device into ovoid or spherical granules, and

[4] the granulated product is dried at a temperature of −50 to 200° C.at atmospheric pressure or under reduced pressure.

The granules can have any desired geometric form; for example, they canbe cylindrical, ovoid or spherical. The granules preferably have anon-angular, rounded geometric form. With particular preference thegranules are essentially spherical, which can be achieved by theoptional step [3]. If spherical, the granules generally have a particlesize with a diameter from 0.5 to 4 mm. Cylindrical and ovoid granulesgenerally have a diameter from 1 to 3 mm and a length from 1 to 10 mm.

The granules preferably have a particle size with a diameter from 1 to 4mm. With particular preference the granules have a particle size with adiameter from 1 to 2.5 mm. If the granules are not spherical, they havea particle size with a theoretical diameter$\left( \sqrt[3]{\frac{6 \times {volume}}{\pi}} \right)$

from 1 to 2.5 mm.

Within the granules, the organic pigment and the binder preferably forman essentially homogeneous mixture.

The organic pigment can be an individual compound from any desiredpigment class, or else a mixture of two or more compounds from the sameor from different pigment classes, and can be present in any desired,known crystal modification, which is advantageously retained in thecourse of the process of the invention, or else can be a solid solution.

Examples of suitable pigment classes are the diketopyrrolopyrroles,quinacridones, perylenes, dioxazines, anthraquinones, indanthrones,flavanthrones, indigos, thioindigos, quinophthalones, isoindolinones,isoindolines, phthalocyanines, metal complexes and azo pigments.

Preferred pigments are diketopyrrolopyrroles, quinacridones, perylenes,dioxazines, indanthrones, flavanthrones, isoindolinones andphthalocyanines and also aminoanthraquinones and disazo condensationpigments. Particularly preferred pigments are diketopyrrolopyrroles,quinacridones and phthalocyanines. Very particularly preferred pigmentsare diketopyrrolopyrroles.

Preferred perylenes are of the formula (Ia), (Ib), (Ic) or (Id),

in which R₁ is hydrogen, C₁-C₆alkyl, phenyl or benzyl or is phenethylwhich is unsubstituted or substituted by halogen, C₁-C₄alkyl orC₁-C₄alkoxy.

Preferred quinacridones are of the formula (II),

in which R₁ is hydrogen, C₁-C₆alkyl, phenyl or benzyl or is phenethylwhich is unsubstituted or substituted by halogen, C₁-C₄alkyl orC₁-C₄alkoxy, and R₂ and R₃ independently of one another are hydrogen,halogen, C₁-C₁₈alkyl, C₁-C₄alkoxy or phenyl.

Preferred dioxazines are of the formula (III),

in which R₁ is hydrogen, C₁-C₆alkyl, phenyl or benzyl or is phenethylwhich is unsubstituted or substituted by halogen, C₁-C₄alkyl orC₁-C₄alkoxy, and R₄ is hydrogen, halogen or C₁-C₁₈alkyl.

Preferred isoindolinones are of the formula (IVa) or (IVb),

in which R₅, R₆, R₇ and R₈ independently of one another are hydrogen,C₁-C₁₈alkyl, C₁-C₄alkoxy, halogen or trifluoromethyl.

Preferred flavanthrones are of the formula (VI),

in which R₂ and R₃ independently of one another are hydrogen, halogen,C₁-C₁₈alkyl, C₁-C₄alkoxy or phenyl.

Preferred indanthrones are of the formula (VI),

in which R₂ and R₃ independently of one another are hydrogen, halogen,C₁-C₁₈alkyl, C₁-C₄alkoxy or phenyl.

Preferred phthalocyanines are of the formula (VII),

in which M is H₂, Zn, Cu, Ni, Fe, Ti(═O) or V(═O),

Z is halogen and

y is 0 or an integer from 1 to 4.

Preferred pyrrolo(3,4-c)pyrroles are of the formula (VIII),

in which R₁ is hydrogen, C₁-C₆alkyl, phenyl or benzyl or is phenethylwhich is unsubstituted or substituted by halogen, C₁-C₄alkyl orC₁-C₄alkoxy, and

G₁ and G₂ independently of one another are a group of the formula

in which R₉ and R₁₀ independently of one another are hydrogen, halogen,C₁-C₁₈alkyl, C₁-C₁₈, C₁-C₁₈alkylthio, C₁-C₁₈alkylamino,C₂-C₁₈dialkylamino, —CN, —NO₂, phenyl, trifluoromethyl, C₅-C₆cycloalkyl,imidazolyl, pyrazolyl, triazolyl, piperazinyl, pyrrolyl, oxazolyl,benzoxazolyl, benzothiazlyl, benzimidazolyl, morpholinyl, piperidinyl,pyrrolidinyl, —C═N—(C₁-C₁₈alkyl) or

R₁₁ and R₁₂ independently of one another are hydrogen, halogen,C₁-C₆alkyl, C₁-C₆alkoxy or —CN,

R₁₃ and R₁₄ independently of one another are hydrogen, halogen orC₁-C₆alkyl,

L is —CH₂—, —CH(CH₃)—, —C(CH₃)₂—, —CH═N—, —N═N—, —O—, —S—, —SO—, —SO₂—or —NO₁₅— and

R₁₅ is hydrogen or C₁-C₆alkyl.

The preferred aminoanthraquinone pigment is of the formula (IX)

Preferred indigo derivatives are of the formula (X),

in which R₁₆ is hydrogen, CN, C₁-C₄alkyl, C₁-C₄alkoxy or halogen.

Preferred isoindolines are of the formula (XIa), (XIb) or (XIc),

in which R₁₇ is hydrogen, C₁-C₁₈alkyl, benzyl or a group

and

R₁₇′ is a group

where R₁₈, R₁₉, R₁₇′ and R₁₈′ independently of one another are hydrogen,C₁-C₁₈alkyl, C₁-C₄alkoxy, halogen or trifluoromethyl.

Any halogen substituents are, for example, iodine, fluorine, especiallybromine and preferably chlorine.

C₁-C₄Alkyl is, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl,sec-butyl or tert-butyl, in the case of C₁-C₆alkyl additionally, forexample, n-amyl, tert-amyl or hexyl, and in the case of C₁-C₁₈alkylagain additionally, for example, heptyl, octyl, 2-ethylhexyl, nonyl,decyl, dodecyl, tetradecyl, hexadecyl or octadecyl.

C₅-C₆Cycloalkyl is, for example, cyclopentyl and, in particular,cyclohexyl.

C₁-C₄Alkoxy is, for example, methoxy, ethoxy, n-propoxy, isopropoxy orbutyloxy, and C₁-C₁₈alkoxy is in addition, for example, hexyloxy,decyloxy, dodecyloxy, hexadecyloxy or octadecyloxy.

C₁-C₁₈Alkylthio is, for example, methylthio, ethylthio, propylthio,butylthio, octylthio, decylthio, hexadecylthio or octadecylthio.

C₁-C₁₈Alkylamino is, for example, methylamino, ethylamino, propylamino,hexylamino, decylamino, hexadecylamino or octadecylamino.

C₂-C₁₈Dialkylamino is, for example, dimethylamino, diethylamino,methylpropylamino, ethylhexylamino, methyldecylamino, dioctylamino orethylhexadecylamino, the carbon atoms of both alkyl radicals beingcounted together.

In the case of the perylenes of the formula (la) or (Ic), thequinacridones of the formula (II), the dioxazines of the formula (III)and the pyrrolo(3,4-c)pyrroles of the formula (VIII) particularpreference is given to those in which R₁ is hydrogen.

Particularly preferred quinacridones of the formula (II) are those inwhich R₁ is hydrogen and R₂ and R₃ independently of one another arehydrogen, methyl, chlorine or methoxy.

Particularly preferred phthalocyanines of the formula (VII) are those inwhich M is H₂, Zn or Cu, and Z is chlorine or bromine.

Particularly preferred pyrrolo(3,4-c)pyrroles of the formula (VIII) arethose in which R₁ is hydrogen and G₁ and G₂ independently of one anotherare each a group of the formula

R₂₀ is fluorine, chlorine, cyano, nitro, trifluoromethyl, C₁-C₄alkyl,Cc-C₄alkoxy, C₁-C₄alkylamino or C₁-C₄dialkylamino, and, of these,especially those in which R₂₀ is chlorine. A preference quite out of theordinary is given to1,4diketo-3,6-di(4′-chlorophenyl)-2,5-dihydropyrrolo[3,4-c]pyrrole.

The organic pigment used in accordance With the invention has a particlesize from 0.01 to 10 μm. This means that at least 90% by weight of theparticles have this particle size. The organic pigment preferably has amean particle size of from 0.2 to 2 μm. With particular preference theorganic pigment has a narrow particle size distribution, in other wordsat least 80% by weight of the particles have a particle size which iswithin a range whose extent is not more than one power of ten, forexample between 0.5 and 5 μm or between 0.2 and 2 μm. A narrow particlesize distribution can be obtained by methods known to the skilledworker, for example by treatment in a polar inert liquid at elevatedtemperature. Appropriate liquids, temperatures and durations for thistreatment, which may be very different depending on the pigment, areknown for all pigment classes and for many individual pigments.

The binder has from 2 to 7 mol of carboxyl groups per 1000 g ofsubstance. The binder generally contains 30-1 00% by weight, preferablyat least 60% by weight, of at least one organic acid, it being possiblefor the remainder of the binder to be neutral. The organic acid can, forexample, be a saturated or unsaturated, long-chain pure acid, or amixture thereof, for example a homologue mixture. Long-chain acids arethose in which there is at least one linear chain consisting of 8 Catoms. Preference is given to abietic acid and to acid mixturescomprising at least 5% by weight of abietic acid.

The neutral remainder of the binder may comprise, for example,substances which usually appear as impurities in the acids used.However, it is likewise possible to add relatively small amounts of atexture enhancer to the organic acid. The texture enhancer, if added, isa constituent of the binder; its amount is not more than 50% by weight,preferably not more than 10% by weight, based on the overall binder. Thetexture enhancer can, for example, be an amide or a metal salt of anorganic acid having at least 18 C atoms, an alkylphenol or an aliphaticalcohol, or a plasticizer or a wax. Known texture enhancers are, forexample, stearamide or behenamide, magnesium stearate or magnesiumbehenate, stearyl alcohol, aliphatic 1,2-dihydroxy compounds having 8 to22 C atoms, such as 1,2-dodecanediol, dibutyl phthalate or beeswax.

The binder consists preferably of a mixture of naturally occurring acidshaving 8 to 30 carbon atoms and naturally occurring terpene derivatives,and can be obtained, for example, by extraction from naturally occurringwoods. For example, this mixture can be resin or Staybelite Resin™(Hercules Inc., Wilmington/Del./USA). The binder particularly preferablyhas a melting point of 70-300° C. and, with very particular preference,a melting point of 90-200° C.

The exact amount of the binder depends on what is required of thegranules. If granules with very high mechanical loadability arerequired, then the amount of binder is preferably 5-10% by weight,particularly preferably 5-8% by weight. If, on the other hand, universalgranules of very good compatibility in as wide as possible a range ofapplications (for example in coatings) are desired, then the amount ofbinder is preferably 0.5-2% by weight. Very particular preference isgiven to granules which contain less than 0.5% by weight of binder orwhich are even totally free from binder. Although in the latter case itis unclear how the pigment particles are held together within thegranules, it has been found, very surprisingly, that even binder-freegranules prepared in accordance with the invention have a highlyremarkable mechanical stability.

The neutral non-ionic emulsifier can be, for example, a copolymer ofethylene oxide and propylene oxide, a fatty alcohol ethoxylate or analkylphenol ethoxylate, for example an emulsifier of the Emulan® series(BASF). The amount of emulsifier is preferably 0.3-1% by weight.

Binder and emulsifier are independent of one another and both areoptional. Depending on the desired granule properties it is possible touse, as desired, binder, emulsifier, both binder and emulsifier, orneither binder nor emulsifier. The binders and emulsifiers listed areused in the process according to the invention, if at all, in the statedconcentrations, which begin at zero per cent by weight (corresponding tocomplete absence). The preferred overall amount of binder and emulsifieris preferably 0.3-5% by weight.

The C₁-C₈alcohol may be if desired, for example, methanol, ethanol,n-propanol, isopropanol or a butanol, and can be used in pure form or,in particular, as aqueous mixtures. Preference is given toC₁-C₄alcohols, especially methanol, ethanol or isopropanol; methanol isparticularly preferred.

The C₃-C₈ketone may be if desired, for example, acetone, ethyl methylketone, methyl propyl ketone or cyclohexanone, and can be used in pureform or, in particular, as aqueous mixtures. Preference is given toC₃-C₆ketones, especially acetone or ethyl methyl ketone; ethyl methylketone is particularly preferred.

However, it is generally very particularly preferred to use in stage [1]from 90 to 100% by weight of water, based on the overall amount ofwater, C₁-C₈alcohol and C₃-C₈ketone, it being possible to use, inparticular, water alone, which can for example be of a defined quality,for example deionized water. As an exception, highly polar pigments suchas pigments having at least one primary amino group, for example theaminoanthraquinone of formula (IX), are preferably granulated at a lowerconcentration of water, particularly preferred at from 30 to 60% byweight of water, based on the overall amount of water, C₁-C₈alcohol andC₃-C₈ketone.

If a mixture of water, a C₁-C₈alcohol and/or a C₃-C₈ketone is used, itis preferably an azeotropic mixture. This makes it possible to reuse themixture easily in an advantageous manner.

The C₁-C₃amine may, if desired, be methylamine, dimethylamine,ethylamine, trimethylamine, ethylmethylamine, n-propylamine orisopropylamine. Preference is given to C₁-C₃amines having a very lowboiling point, and particular preference to methylamine. With veryparticular preference, however, ammonia rather than a C₁-C₃amine is usedin stage [1]. Ammonia is understood as meaning gaseous ammonia; insteadit is of course also possible to use liquid ammonia—in this case,however, the water of the liquid ammonia also counts as added water. Thepreferred amount of ammonia or C₁-C₃amine is about 1 mol per mole ofcarboxyl groups in the binder, so that the binder is just completelyneutralized.

The mixing of the pigment with the water and/or C₁-C₈alcohol and/or withthe C₃-C₈ketone, the emulsifier, the binder and the ammonia orC₁-C₃amine can be effected in any known manner, for example in a mixingapparatus. Useful mixing apparatus is that in which the pigment issubjected to a maximum pressure which is lower than the maximum pressurearising in stage [2] of the process. The skilled worker is aware ofnumerous mixers imposing little mechanical stress, for example thosedescribed in Perry's Chemical Engineer's Handbook (6^(th) Ed.,McGraw-Hill Book Company). Commercially available annular bed mixers arepreferred.

The pigment can be employed in dry form or else in the form of moistproduct, for example a moist filter cake; in the latter case, the wateror C₁-C₈alcohol or C₃-C₈ketone present in the moist product also countsas added water or alcohol or ketone. If the moist product issufficiently moist it may be possible to do entirely without additionalmoistening media. For example, a pigment filter cake with 47.9% residualmoisture corresponds to the addition of 91.9% by weight, and one with35.1% residual moisture to the addition of 54.1% by weight, of water tothe dry pigment. Preferably, however, a dry pigment of knownspecifications is employed. The binder can be employed dry or in theform of a solution of the ammonium salt. In the latter case, forexample, the binder is stirred beforehand together with ammonia or aC₁-C₃amine in water, C₁-C₈alcohol, C₃-C₈ketone or a mixture thereof, atroom temperature or at a temperature which is between room temperatureand the melting point of the binder, under atmospheric orsuperatmospheric pressure, until a solution is formed. Binder solutionsare preferably prepared at room temperature.

The form and sequence in which the ingredients are mixed in isessentially unimportant. What is important, however, is that the mixtureis substantially homogeneous after mixing. It is therefore preferred toemploy the binder in the form of a solution of the ammonium salt, inwhich case all of the water or C₁-C₄alcohol, or just part of it, can beused to prepare this solution.

It is particularly preferred to meter in the dry pigment continuously atthe entrance of the mixer while at the same time spraying on anammoniacal aqueous solution of the binder in the required amount. Thisprocess lends itself particularly well to full automation by methodsknown per se. The mixed product can be processed further immediately orlater in stage [2] of the process, it being preferred to follow stage[1] directly by stage [2].

Pressing takes place mechanically in a continuously operating apparatuswhich consists at least of a conveying device and a shaping section withapertures. The conveying device is not subject to any particularrequirements, other than that the mixture to be pressed should not besubjected therein to any pressure exceeding 10 bar. Conventionalconveying devices can be used, for example one or more rotating screws.A twin screw is the preferred conveying device.

The apertures through which the mixture is pressed can in principle haveany desired cross-section. Apertures with a non-angular cross-sectionare preferred. By this are meant rounded, for example elliptical or,preferably, circular apertures which have no angles. The aperturespreferably measure from 0.5 to 2.5 mm in the shortest axis. Theapertures can, for example, be punched out or burnt with a laser beam.while the circular apertures can in addition, and preferably, bedrilled. It is preferred to have a large number of apertures made atregular intervals. The preferred diameter of circular apertures isdependent on the binder and at 0-3% by weight of binder is from 0.5 to1.5 mm, at 3-10% by weight of binder, on the other hand, from 1.0 to 2.5mm.

The shaping section with the apertures has any desired form which isneither planar nor cylindrical. If use is made in fact of a planar sievearranged at right angles to the conveying device, then the pressuregenerally exceeds the maximum pressure which is critical to theinvention, and the granules do not have the advantages of the invention.It is therefore critical for the shaping section with the apertures tohave a three-dimensional curvature, for example a hollow truncated coneor a hollow dome. On the other hand, the material to be shaped is oftenpressed in a highly irregular manner if the sieve is a hollow cylinder,and in this case increases in pressure, possibly exceeding the maximumpressure which is critical to the invention, occur readily for shortperiods, and at least some of the material likewise lacks the advantagesof the invention. The shaping section is preferably hemispherical.

The preferred apparatus constructed in accordance with the features ofthe invention comprises radial extruders and, with particularpreference, dome extruders, which are obtainable commercially innumerous designs. Since the build-up of pressure is a function of therotational speed of the conveying screw, the apparatus should beoperated at a lower rotational speed than the maximum speed,corresponding to a reduced throughput, where this appears necessary onthe basis of the desired maximum pressure.

In a radial extruder the pressure increases in the direction of the coneapex. In this case it may be that the pressure at the apex of theshaping section threatens to exceed 10 bar. In general, therefore, theapex of the shaping section should have an additional aperture, whichshould be designed or set such that the desired pressure is notexceeded. The small amount of material emerging from this additionalregulatable aperture can in fact be recycled but only if it has beenexposed to a maximum pressure of not more than 10 bar.

Recycling, however, is generally not advisable. This problem does notarise in the case of the dome extruder, which is particularly preferred.

The pressure in the shaping section is preferably from 1 to 5 bar,particularly preferably from 1.1 to 3 bar. The cylindrical extrudategenerally breaks up of its own accord on emergence from the shapingsection into pieces with a length of about 2 to 6 mm, which judiciouslyshould not be allowed to stand for any length of time. The cylindricalgranules are preferably processed further directly.

The rotating device which converts the cylindrical granules intospherical granules can be, for example, a plate, a hollow cylinder orthe like. The cylindrical material emerging from the extruder ispreferably passed directly onto roughly the centre of the rotatingdevice, centrifugal force setting the cylindrical granules into arolling movement and so converting them into more or less sphericalgranules.

Conversion into ovoid or spherical granules is optional. However, it hasbeen found that the performance advantages of the invention are greaterif the granules are ovoid or spherical. Preferably, therefore, thisoptional stage is implemented.

The granulated product is dried in known manner at the statedtemperature and under the state d pressure. Drying can be operatedbatchwise or continuously, in the latter case the material to be driedbeing conveyed, for example on a conveyor belt, through an oven which isopen at both ends and is at a temperature of 100-200° C. In the courseof drying both the water or the C₁-C₄alcohol and, if present, theammonia or the C₁-C₃amine are released, and are stripped off ifnecessary. The vapours are preferably taken off under suction andcondensed, with the condensates being recycled. Instead of drying in anoven, however, it is also possible to use any other drying method, forexample freeze-drying.

The whole of the process of the invention is preferably operatedcontinuously.

The pigment granules prepared in accordance with the invention arecoarse and highly concentrated, extremely dust-free and readilydispersibile. The physical parameters of the pigment particles presentwithin the pigment granules are hardly changed relative to those of thepigment particles in the initial pigment powder. In general, therefore,organic pigment present in the pigment granules likewise has a particlesize of from 0.01 to 10 μm. The organic pigment enclosed in the pigmentgranules preferably has a narrow particle size distribution. Furtherpreferred pigment granules include those obtained by the abovementionedpreferred embodiments of the process of the invention.

The invention therefore also relates to pigment granules with a particlesize from 0.5 to 4 mm which consist of at least 90% by weight of atleast one organic pigment and from 0 to 10% by weight of a binder havingfrom 2 to 7 mol of carboxyl groups per 1000 g and from 0 to 5% by weightof a neutral emulsifier which does not form ions and which dissolves togive a clear solution in water or a C₁-C₄alcohol at a concentration ofat least 10 g/100 ml, the binder and the emulsifier together accountingfor not more than 10% by weight and all percentages by weight beingbased on the overall amount of pigment granules, wherein the pigmentpresent in the pigment granules essentially has a particle size of from0.01 to 10 μm.

To determine the particle size of the pigment present therein, thegranules can be treated with ultrasound in a liquid which wets but doesnot dissolve the pigment, but which may dissolve or break up the othercomponents of the granules, so as to give a homogeneous dispersion ofthe pigment. The particle size distribution of the dispersed pigment canthen be determined, for example, by disc centrifuging. A suitableapparatus for this, for example, is the Joyce-Loebl disc centrifuge DCF4. The requirements regarding sample preparation and the determinationof the particle size distribution are very well known to the skilledworker in the field of particle measurement. The techniques are alsodescribed comprehensively in relevant textbooks [cf. e.g. Terence Allen,Particle Size Measurement, !, (Chapman and Hall, London, New York1981)].

On account of the properties highlighted above, the pigment granules ofthe invention are especially suitable, in an effective amount forcolouring, for pigmenting high molecular mass organic material,especially plastics and coatings.

The high molecular mass organic material for whose pigmenting thepigment granules of the invention can be used can be of natural orsynthetic origin. High molecular mass organic materials usually havemolecular weights from about 10³ to 10⁷ g/mol or more. They may be, forexample, natural resins, drying oils, rubber or casein or naturalsubstances modified from these, such as chlorinated rubber, oil-modifiedalkyd resins, viscose, cellulose ethers or esters, such asethylcellulose, cellulose acetate, cellulose propionate, celluloseacetobutyrate or nitrocellulose, but especially fully synthetic organicpolymers (thermosets and thermoplastics) as are obtained by additionpolymerization, condensation polymerization or polyaddition. From theclass of the addition polymerization resins mention may be madeprimarily of polyolefins, such as polyethylene, polypropylene orpolyisobutylene, and substituted polyolefins, such as polymers of vinylchloride, vinyl alcohol, vinyl acetate, butyl acetate, styrene,acrylonitrile, acrylic or methacrylic acid, acrylic or methacrylicesters or butadiene, and also copolymers of the monomers mentioned,especially ABS or EVA.

From the series of the polyaddition resins and condensationpolymerization resins mention may be made of the condensates offormaldehyde with phenols, known as phenolic resins, and the condensatesof formaldehyde with urea, thiourea and melamine, known as aminoresins,the polyesters which are used as paint resins, and indeed both saturatedresins, for example alkyd resins, and unsaturated resins, for examplemaleate resins, and also the linear polyesters and polyamides,polyurethanes or silicones.

The high molecular mass compounds mentioned can be present individuallyor in mixtures, as plastic masses or melts. They can also be in the formof their monomers or in the polymerized state in dissolved form as filmformers or binders for coating materials or printing inks, for examplelinseed oil varnish, nitrocellulose, alkyd resins, melamine resins andurea-formaldehyde resins or acrylic resins.

The pigment granules of the invention can be added in any amounteffective for colouring to the high molecular mass organic material thatis to be pigmented. A pigmented composition judiciously contains 0.1-30%by weight, preferably 1-20% by weight, of pigment granules according tothe invention, based on the high molecular mass organic material that isto be pigmented.

For pigmenting organic materials the pigment granules of the inventioncan be used individually. It is likewise possible, however, in order toobtain different shades or colour effects, to add other colouringconstituents, such as white, coloured, black or special-effect pigments,in any desired amounts to the organic substances in addition to thepigment granules of the invention.

The pigmenting of the high molecular mass organic substances with thepigment granules of the invention takes place, for example, by mixingsuch pigment granules into these substrates using roll mills, mixers ormilling apparatus. The pigmented material is subsequently brought intothe desired end form by techniques known per se such as calendering,compression moulding, extrusion, spreading, casting or injectionmoulding. All additives customary in the plastics industry, for exampleplasticizers, fillers or stabilizers, can be incorporated into thepolymers in customary amounts before or after the incorporation of thepigment. In order to produce non-rigid mouldings or to reduce theirbrittleness it is particularly desirable to incorporate plasticizers,for examples esters of phosphoric, phthalic or sebacic acid, into thehigh molecular mass compounds before they are shaped.

For pigmenting coating materials and printing inks the high molecularmass organic materials and the pigment granules of the invention, aloneor together with customary additives, for example fillers, otherpigments, siccatives or plasticizers, are finely dispersed or dissolvedin an organic solvent or solvent mixture suitable for all of them. Apossible procedure here is to disperse or dissolve the individualcomponents alone, or else two or more of them together, and only then tocombine all of the components,

The colourings obtained, for example in plastics, coating materials orprinting inks, preferably in coating materials or printing inks and,with particular preference, in coating materials, are notable forexcellent properties which are at least equal to those of the powderpigments and in many cases indeed are superior.

Where the high molecular mass material to be pigmented is a coatingmaterial, it is in particular a speciality coating material, with veryparticular preference an automotive coating material.

The examples which follow illustrate the invention (in the examples theparts and percentages are in each case by weight):

EXAMPLE 1

260 kg of3,6-di-(4′-chlorophenyl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dionemeeting pigment-grade specification are pasted up homogeneously with 189kg of deionized water in a conventional annular bed mixer (K-TT™, DraisAG, Mannheim/Germany) to give a formable mass having a solids content of58%. This moist mass is extruded through a hemispherical shaping sectionhaving perforations of 1 mm in diameter in a radial extruder (DG-L1™,Fitzpatrick Co. Europe NV, St.-Niklaas/Belgium) at a conveying speed of40-50 rpm with a throughput of about 120 kg/h. The cylindrical extrudateparticles are then shaped to spheroids in a rounding stage on agranulating plate, and these spheroids are dried in a convection oven at120° C. to a residual moisture content of <1%. Granules are obtainedwhich are markedly lower in dust than the pigment employed yet whilehaving similar ease of dispersibility. Incorporated by conventionalmethods in an alkyd/melamine varnish or in flexible PVC, these granulesgive colouratings which are essentially similar to those provided by thepulverusent pigment.

EXAMPLE 2A

The procedure of Example 1 is repeated but using as raw material amixture, obtainable in analogy to IN-156'867 and U.S. Pat. No.4,264,552, comprising 90% C.I. Pigment Red 177 [65300] and 10%Staybelite Resin™. 300 parts of this dry mixture are formed into a pastewith 200 parts of deionized water (i.e. 74.1% based on the pigment) and9 parts of trimethylamine in an annular bed mixer, and this paste isextruded to filaments of 0.70 mm in diameter in a radial extruder at alow extrusion pressure. The extruded particles are rounded to givespheroids of about 1 mm which are dried in a vacuum oven at 100° C.under reduced pressure. The resulting granules have very goodproperties.

EXAMPLE 2B

The procedure of Example 2A is repeated except that filaments of 1.2 mmin diameter are extruded. The extruded particles are rounded tospheroids of about 2 mm. The resulting granules have very goodproperties.

EXAMPLE 2C

The procedure of Example 2B is repeated except that non-ionic processwater (24° dh [German hardness]) is used. The resulting granules havevery good properties.

EXAMPLE 3A

The procedure of Example 1 is repeated but using as raw material pureC.I. Pigment Red 220 [20055]. 310 parts of this dry pigment are formedinto a paste with 190 parts of deionized water in an annular bed mixer,and this paste is extruded in a radial extruder at low extrusionpressure. The extruded particles are rounded into spheroids and dried ina vacuum oven at 110° C. under reduced pressure. The resulting granuleshave very good properties.

EXAMPLE 3B

The procedure of Example 3A is repeated, except that 190 parts of drypigment are formed into a paste with 143 parts of a 7% strength solutionof Emulan OSN™ (BASF, Leverkusen/Germany) in deionized water in anannular bed mixer. The resulting granules have very good properties.

EXAMPLE 3C

The procedure of Example 3A is repeated, except that 195 parts of drypigment are formed into a paste with 14 parts of a 7% strength solutionof Emulan OSN™ in deionized water and 126 parts of deionized water in anannular bed mixer. The resulting granules have very good properties.

EXAMPLE 4A

The procedure of Example 1 is repeated but using as raw material pureC.I. Pigment Yellow 93 [20710]. 300 parts of this dry pigment are formedinto a paste with 200 parts of deionized water in an annular bed mixer,and this paste is extruded in a radial extruder at low extrusionpressure. The extruded particles are rounded into spheroids and dried ina vacuum oven at 100° C. under reduced pressure. The resulting granuleshave very good properties.

EXAMPLE 4B

The procedure of Example 4A is repeated, except that 190 parts of drypigment are formed into a paste with 143 parts of the 7% strengthsolution of Emulan OSN™ in an annular bed mixer. The resulting granuleshave very good properties.

EXAMPLE 4C

The procedure of Example 4A is repeated, except that 195 parts of drypigment are formed into a paste with 14 parts of a 7% strength solutionof Emulan OSN™ (BASF, Leverkusen/Germany) in deionized water and 126parts of deionized water in an annular bed mixer. The resulting granuleshave very good properties.

EXAMPLE 5A

The procedure of Example 1 is repeated but using as raw material pureC.I. Pigment Orange 64 [12760]. 300 parts of this dry pigment are formedinto a paste with 200 parts of deionized water in an annular bed mixer,and this paste is extruded in a radial extruder at low extrusionpressure. The extruded particles are rounded into spheroids and dried ina vacuum oven at 100° C. under reduced pressure. The resulting granuleshave very good properties.

EXAMPLE 5B

The procedure of Example 5A is repeated, except that 195 parts of drypigment are formed into a paste with 71 parts of a 7% strength solutionof Emulan OSN™ (BASF, Leverkusen/Germany) in deionized water and 64parts of deionized water in an annular bed mixer. The resulting granuleshave very good properties.

EXAMPLE 5C

The procedure of Example 5B is repeated except that, during shaping inthe annular bed mixer, 26 parts of a solution consisting of 5 parts ofStaybelite Resins, 6 parts of 25% aqueous ammonia solution and 15 partsof deionized water are added as well. The resulting granules have verygood properties.

EXAMPLE 6A

The procedure of Example 1 is repeated but using as raw material pureC.I. Pigment Red 144 [20735]. 260 parts of this dry pigment are formedinto a paste with 240 parts of deionized water in an annular bed mixer,and this paste is extruded in a radial extruder at low extrusionpressure. The extruded particles are rounded into spheroids and dried ina vacuum oven at 100° C. under reduced pressure. The resulting granuleshave very good properties.

EXAMPLE 6B

The procedure of Example 6A is repeated except that the pigment is usedin the form of a water-containing press cake comprising 44.7% residualmoisture. 372 parts of this moist press cake are formed into a pastewith 24 parts of deionized water in an annular bed mixer, and the pasteis extruded in a radial extruder at a low extrusion pressure. Theresulting granules have very good properties.

EXAMPLE 7A

The procedure of Example 1 is repeated but using as raw materialCINQUASIA Magenta B RT-343-D™ (C.I. Pigment Red 202 [73907], Ciba-GeigyAG, Basle/Switzerland). 200 parts of this dry pigment are formed into apaste with 165 parts of deionized water in an annular bed mixer, andthis paste is extruded in a radial extruder at low extrusion pressure.The extruded particles are rounded into spheroids and dried in a vacuumoven at 100° C. under reduced pressure. The resulting granules have verygood properties.

EXAMPLE 7B

The procedure of Example 7A is repeated except that 532 parts of drypigment are formed into a paste with 318 parts of a solution consistingof 29 parts of Staybelite Resin™, 198 parts of 25% strength aqueousammonia solution and 91 parts of deionized water in an annular bedmixer. The resulting granules have very good properties.

EXAMPLE 7C

The procedure of Example 7B is repeated, except that Staybelite Resin™is used not in the form of a solution but as a fine powder and ischarged directly to the annular bed mixer at the same time as thepigment, the aqueous ammonia solution and the water. The resultinggranules have very good properties.

EXAMPLE 8A

The procedure of Example 1 is repeated but using as raw materialCINQUASIA Magenta RT-243-D™ (C.I. Pigment Red 202 [73907], Ciba-GeigyAG, Basle/Switzerland). 345 parts of this dry pigment are formed into apaste with 129 parts of deionized water in an annular bed mixer, andthis paste is extruded in a radial extruder at low extrusion pressure.The extruded particles are rounded into spheroids and dried in a vacuumoven at 100° C. under reduced pressure. The resulting granules have verygood properties.

EXAMPLE 8B

The procedure of Example 8A is repeated except that 570 parts of drypigment are formed into a paste with 251 parts of a solution consistingof 30 parts of Staybelite Resin™, 205 parts of 25% strength aqueousammonia solution and 16 parts of deionized water in an annular bedmixer. The resulting granules have very good properties.

EXAMPLE 8C

The procedure of Example 8A is repeated except that 570 parts of drypigment are formed into a paste with 205 parts of a solution consistingof 30 parts of Staybelite Resin™, 21 parts of 25% strength aqueousammonia solution and 154 parts of deionized water in an annular bedmixer. The resulting granules have very good properties.

EXAMPLE 9A

The procedure of Example 1 is repeated but using as raw materialCINQUASIA Violet R RT-101-D™ (C.I. Pigment Violet 19 [73900], Ciba-GeigyAG, Basle/Switzerland). 335 parts of this dry pigment are formed into apaste with 295 parts of deionized water in an annular bed mixer, andthis paste is extruded in a radial extruder at low extrusion pressure.The extruded particles are rounded into spheroids and dried in a vacuumoven at 100° C. under reduced pressure. The resulting granules have verygood properties.

EXAMPLE 9B

The procedure of Example 9A is repeated except that 594 parts of drypigment are formed into a paste with 560 parts of a solution consistingof 6 parts of Staybelite Resin™, 41 parts of 25% strength aqueousammonia solution and 513 parts of deionized water in an annular bedmixer. The resulting granules have very good properties.

EXAMPLE 9C

The procedure of Example 9A is repeated except that 594 parts of drypigment are formed into a paste with 550 parts of a solution consistingof 6 parts of Staybelite Resin™, 3 parts of 25% strength aqueous ammoniasolution and 541 parts of deionized water in an annular bed mixer. Theresulting granules have very good properties.

What is claimed is:
 1. A process for preparing organic pigment granuleswith a particle size from 0.5 to 4 mm, which consist of at least 90% byweight of at least one organic pigment with a particle size from 0.01 to10 μm and from 0 to 10% by weight of a binder having from 2 to 7 mol ofcarboxyl groups per 1000 g and from 0 to 5% by weight of a neutralemulsifier which does not form ions and which dissolves to give a clearsolution in water or a C₁-C₄alcohol at a concentration of at least 10g/l 00 ml, the binder and the emulsifier together accounting for notmore than 10% by weight and all percentages by weight being based on theoverall amount of pigment granules, wherein [1] the pigment is mixedwith 54-92% by weight of water, a C₁-C₄alcohol, a C₃-C₈ketone or amixture thereof, based on the dry pigment, with the binder and 0.8-20mol of ammonia or a C₁-C₃amine, per mole of carboxyl groups in thebinder, and with the emulsifier; [2] this mixture is pressed in acontinuously operating apparatus through one or more apertures eachhaving a size of 0.2-5.0 mm², the apparatus consisting of at least oneconveying device and a shaping section comprising the apertures, andbeing constructed, and operated with a throughput, such that thepressure in its shaping section does not exceed 10 bar; [3] if desired,the cylindrical granules emerging from the dies are converted on arotating device into ovoid or spherical granules, and [4] the granulatedproduct is dried at a temperature of −50 to 200° C. at atmosphericpressure or under reduced pressure.
 2. A process according to claim 1,in which the granules are essentially spherical and have a particle sizewith a diameter from 0.5 to 4 mm.
 3. A process according to claim 1, inwhich the pigment is a diketopyrrolopyrrole, quinacridone orphthalocyanine pigment.
 4. A process according to claim 3 which thepigment is a diketopyrrolopyrrole of the formula (VIII)

in which R₁ is hydrogen, C₁-C₆alkyl, phenyl or benzyl or is phenethylwhich is unsubstituted or substituted by halogen, C₁-C₄alkyl orC₁-C₄alkoxy, and G₁ and G₂ independently of one another are a group ofthe formula

in which R₉ and R₁₀ independently of one another are hydrogen, halogen,C₁-C₁₈alkyl, C₁-C₁₈alkoxy, C₁-C₁₈alkylthio, C₁-C₁₈alkylamino,C₂-C₁₈dialkylamino, —CN, —NO₂, phenyl, trifluoromethyl, C₅-C₆cycloalkyl,imidazolyl, pyrazolyl, triazolyl, piperazinyl, pyrrolyl, oxazolyl,benzoxazolyl, benzothiazolyl, benzimidazolyl, morpholinyl, piperidinyl,pyrrolidinyl, —C═N—(C₁-C₁ ₈alkyl) or

R₁₁ and R₁₂ independently of one another are hydrogen, halogen,C₁-C₆alkyl, C₁-C₆alkoxy or —CN, R₁₃ and R₁₄ independently of one anotherare hydrogen, halogen or C₁-C₆alkyl, L is —CH₂—, —CH(CH₃)—, —C(CH₃)₂—,—CH═N—, —N═N—, —O—, —S—, —SO—, —SO₂— or —NR₁₅— and R₁₅ is hydrogen orC₁-C₆alkyl.
 5. A process according to claim 1, in which the pigment hasa mean particle size from 0.2 to 2 μm.
 6. A process according to claim1, in which the binder contains at least 60% by weight of at least oneorganic acid.
 7. A process according to claim 6, in which the bindercontains at least 5% by weight of abietic acid.
 8. A process accordingto claim 6, in which the amount of the binder is 5-8% by weight.
 9. Aprocess according to claim 6, in which the amount of the binder is0.5-2% by weight.
 10. A process according to claim 1, in which ammoniais used.
 11. A process according to claim 1, in which in stage [1] from90 to 100% by weight of water is used, based on the overall amount ofwater, C₁-C₈alcohol and C₃-C₈ketone.
 12. A process according to claim 1,in which the pigment has at least one primary amino group and in stage[1] from 30 to 60% by weight of water is used, based on the overallamount of water, C₁-C₈alcohol and C₃-C₈ketone.
 13. A method ofpigmenting high molecular mass organic material, in which an amounteffective for colouring of pigment granules prepared by the process ofclaim 1 is used.
 14. A method according to claim 13, in which thepigment granules are used in an amount of 0.1-30% by weight, based onthe high molecular mass organic material that is to be pigmented.
 15. Aprocess according to claim 1, wherein said apparatus used in step 2 is aradial extruder.
 16. A process according to claim 1, wherein saidapparatus used in step 2 is a dome extruder.
 17. A process according toclaim 1, wherein said shaping section in step 2 is neither planar norcylindrical.
 18. A process according to claim 1, wherein said shapingsection in step 2 is a hollow truncated cone.
 19. A process according toclaim 15, wherein said shaping section in step 2 is a hollow truncatedcone.
 20. A process according to claim 1, wherein said shaping sectionin step 2 is hemispherical.
 21. A process according to claim 16, whereinsaid shaping section in step 2 is hemispherical.
 22. A process accordingto claim 1, characterized in that the granules contain less than 33⅓% byvolume of voids.
 23. A process according to claim 1, in which thepigment is a diketopyrrolpyrrole, quinacridone, perylene, dioxazine,indanthrone, flavanthrone, isoindolinone, phthalocyanine,aminoanthraquinone or disazo condensation pigment.